Harvard’s fits utility bundles a lot of file identification tools
and allows you to run them on files easily. It’s used in Samvera
applications for file characterization. If you are importing a large
amount of content into your repository you’ll be starting and stopping
fits many times. The standard way of doing this (running fits.sh over and
over again) isn’t very efficient.

fits includes a script that allows you to run the utility with nailgun.
nailgun is a minimal server that allows you to spin up a JVM for the Java
application and reuse it. The normal way that works is creating and destroying a
JVM instance each time the application is run. If you are starting and stopping
the JVM many thousands of times, that can be inefficient.

nailgun has a client that is written in C and a server jar. To get the nailgun-ified version of fits running on OSX you can install the nailgun client it with brew: